Myocardial Strain and Torsion Quantified by Cardiovascular Magnetic Resonance Tissue Tagging
Studies in Normal and Impaired Left Ventricular Function
Marco J.W. Götte, MD, PhD*, ,*,
Tjeerd Germans, MD,
Iris K. Rüssel, MSc ,
Jaco J.M. Zwanenburg, PhD ,
J. Tim Marcus, PhD,
Albert C. van Rossum, MD, PhD and
Dirk J. van Veldhuisen, FACC, MD, PhD*
* Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
Cardiology
Physics and Medical Technology, Vrije Universiteit Medical Center, and Institute for Cardiovascular Research ICaR-VU, Amsterdam, the Netherlands
Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands
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Figure 1 Basic principle of magnetic resonance tissue tagging. Cardiovascular magnetic resonance tissue tagging. The schematic drawing indicates the short-axis image planes and the magnetically saturated planes perpendicular to the imaging plane (A). During subsequent image acquisition, reduced signal is obtained from the saturated tissue. This results in black lines on the images (B). LV = left ventricle; RV = right ventricle.
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Figure 2 Example of short-axis tagged images during cardiac cycle. Typically, tagging is applied just before contraction starts (end diastole, A). Because the taglines are a temporary property of the tissue, taglines move along with the tissue in which they are created. The lines will deform if the myocardium contracts (B), and become undeformed during relaxation (C). Because of T1 relaxation, the contrast between tagged (dark) and nontagged (bright) myocardium will gradually disappear during subsequent image acquisition (D). LV = left ventricle; RV = right ventricle.
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Figure 3 Representation of myocardial deformation using magnetic resonance tissue tagging. An example of a short-axis image with deformed tagging grid on end systole is shown (A). Tagging is achieved by the application of spatial modulation of magnetization (SPAMM) (18). The tag-tag distance is 7 mm. Using the SPAMMVU software package, the intersection points of the tagging grid can be marked (B) and tracked throughout the cardiac cycle (C). The displacement of these points can be measured, and subsequently the intramural myocardial deformation can be quantified.
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Figure 4 Description of 3-dimensional myocardial strain in the radial/circumferential/longitudinal (rcl) system. Interpretation of myocardial strain (i.e., deformation) depends on the coordinate system used. For clinical purposes, description of strain in the rcl system is preferable. Radial strain (R) indicates deformation of the heart in the radial direction. Positive radial strain during systole reflects the local contribution of the myocardium to wall thickening. Circumferential strain (C) reflects intramural circumferential shortening. A negative value is related to myocyte contraction. Longitudinal strain (l) reflects the regional longitudinal shortening from base to apex.
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Figure 5 Ventricular torsion and untwisting. Torsion and untwisting are the result of contraction and relaxation of the spiraling subepicardial and subendocardial myofibers. The net ventricular torsion is the result of the subepicardial contraction and subendocardial counterbalancing contraction.
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